The present invention relates generally to engine thermostats, more particularly to a programmable thermostat and related system capable of controlling coolant temperature to variable set points.
In order to cool the cylinders and cylinder heads of an automotive engine coolant is pumped through passages within the engine. A thermostat is preferably lodged in one of these passages. At a predetermined temperature the thermostat opens and/or closes thereby permitting the engine coolant to be cooled by the radiator and thereafter returned to the engine. Typically these thermostats fall into two categories the throttle thermostat and the bypass thermostat. The throttle thermostat acts as a variable restriction to the flow of the coolant between the engine and radiator. The bypass thermostat permits the coolant to initially flow in only the engine while the flow to the radiator remains blocked. Once the operating temperature has been reached, the thermostat allows the coolant to flow to the radiator. These thermostats may be located at the engine inlet or outlet.
The prior thermostats automatically open and close about a fixed set point. It is the object of the present invention to provide a thermostat which is programmable thereby providing a variable set point which in turn provides for variable control of the coolant temperature. It is a further object of the present invention to provide a programmable thermostat which can provide increased engine temperatures during warm up and lower engine temperatures during extended running.
Accordingly, the invention comprises a thermostat and system for controlling coolant temperature of an engine, comprising a thermostatic member disposed within a coolant flow passage of an engine comprising valve means, movable between first and second positions for opening and closing the flow passage and when in the first condition inhibiting coolant flow from the engine and when in said second condition permitting the coolant to flow to a heat exchanger. The system includes a thermally responsive element coupled to the valve means. The element is expandable in volume when exposed to a predetermined termperature so as to urge the valve means into the first position to terminate flow therethrough and means for increasing the temperature of the element in response to control signals, above the temperature of the coolant, to cause the element to urge the valve means into the second condition.
Many other objects and purposes of the invention will be clear from the detailed description of the drawings.